The IR Sensor

In this application, we've constructed a chamber of gas whose volume is related to the position of the tunneling membrane. An IR absorber splits the chamber in two, but does have pinholes to allow the pressure of each half to equalize slowly. Similarly, a pinhole on the top membrane gradually allows the gas to match the atmosphere of its surroundings. This acts as a high pass filter and reduces the effect of the environment on the signal.

When the sensor is exposed to an IR signal, the absorber retains the thermal energy and heats the gas. Since the gas is essentially trapped for high frequency signals, by the Ideal Gas Law the pressure of the gas must increase. This pressure on the membrane applies a force, causing the membrane to deflect. As discussed in the general description of our tunneling sensors, we can measure the force on the membrane, which is a measure of the change in IR signal.